The invention relates to dynamoelectric machines and more particularly to slot wedges used to close the coil slots of generator rotors.
The slot wedges are provided in the armature coil slots of rotors to close the rotor slots and retain therein the coils against the large centrifugal forces generated by the coils during operation of the generator. The centrifugal forces taken up by the slot wedges are transmitted by the slot wedges to the rotor teeth which are engaged by the slot wedges. To provide support for the slot wedges the teeth have at their radially outer ends opposite wall sections which project toward one another thereby forming inclined support wall structures for supporting the slot wedges as shown for example in U.S. Pat. Nos. 678,864, 1,741,262, 2,446,708. It has been found, however, that the centrifugal forces are not evenly transmitted from the slot wedges to the rotor teeth. A cross-sectional analysis of generator rotors to yield peak stresses indicated that the tooth tip stresses far exceeded the yield strength of the rotor material. As a result failure of rotor teeth may occur and in fact have occurred resulting in expensive shutdown of the power generator plant for repair.
It is therefore the principal object of the present invention to provide a rotor design with slot wedges which generate only relatively low rotor teeth stresses so as to avoid failure of the rotor teeth without a change in rotor design.